Apparatus for dispensing flowable substances, particularly adhesives, paints, varnishes, and release agents are used, for example, in order to apply adhesives to a substrate, portion by portion. In this connection, application of the adhesives takes place controlled by way of a metering valve, where application as a line, point, spray, spiral, or surface area is particularly possible.
In the processing of flowable substances with metering valves, it is problematic that residues of the substance can accumulate at the outlet of the metering valve, and, particularly if they harden there, can disrupt subsequent operation of the apparatus or can actually bring it to a complete stop.
To avoid such difficulties, an apparatus is proposed in DE 41 13 445 A1.
This apparatus has a nozzle that has an exit opening for dispensing the substances from the nozzle in the region of a free nozzle end. A closure part that can be moved by means of a control element is disposed outside of the nozzle, which part releases the exit opening in an open position and closes the exit opening in a closed position, in the region of a closure part surface that faces the nozzle end. The closure part surface is delimited, in the movement direction of the closure part from the open position to the closed position, by a leading edge, in the leading direction. When the closure part is moved into its closed position, the leading edge therefore makes contact with the free nozzle end first, in each instance, before the closure part contacts the free nozzle end over the full area with its closure part surface, and closes off the exit opening of the nozzle. This action of the free nozzle end on the leading edge during every closing procedure of the closure part leads to increased wear of the leading edge and thereby to a reduced useful lifetime of the apparatus.
An apparatus for dispensing flowable substances is furthermore described in DE 199 36 670 C1. This apparatus has a fixed support, a metering valve connected to this support, having an exit nozzle for the flowable substances, and also an outer closure part for closing the exit opening of the nozzle. In this connection, the closure part is stationary and the metering valve or the nozzle is pivoted relative to the closure part. In this embodiment, as well, a leading edge of the closure part contacts the nozzle in the region of the free nozzle end during the closing procedure, in each instance, resulting in the disadvantage described, that of increased wear of the closure part in the region of the leading edge.
An apparatus for dispensing flowable substances, having a nozzle and a closure part for the nozzle, is furthermore known from EP 0 719 592 A2. In this apparatus, as well, a leading edge of the closure part contacts the nozzle in the region of its free nozzle end when the closure part is moved into its closed position.